Differential Mount Force Analysis

I am designing a differential mount and I am having trouble with the analysis of the forces involved.

I found the force at which my tires will break loose (taking into account acceleration/weight transfer) and did a simple force balance to figure out how much force the chain would be putting on the sprocket at that moment. What I am having trouble with is how to determine how much of that force gets transmitted to the differential mounts. Two of my engineers say that due to statics, the force on the mounts is exactly equal and opposite to the force applied on the chain. I say, due to the fact that we have bearings and it is a torque, not a direct pulling force, only some of the force gets transmitted into the mounts.

This equation seems to back that up http://jeil1120.epart.net/design/template_071/download/09%20load%20calculation.pdf [Broken]

But that assumes that the shaft is already rotating. Which it would not be in the case of a launch.

I'm basically just trying to find the MAX force this thing would be subjected to so it does not break but also want to shave off weight if i can.

here is the basic design, it is not ideal and the bottom is likely overbuilt. but it is what we have for now until FEA gives us more info